To Garold Rib Glueing thoughts

[Erwinpiano]

Hi Garold
Saw your post and enjoyed your enthusiasm. It takes that and much desire to
take this road less traveled by.On the subject of presses etc. I use a go
bar deck with a steeper than 60 ft. radius ( actually about 50 OR LESS) I'm
also crowning my ribs less than some of my associates and drying my panels a
little bit more .I do end up with the 60 ft.ish crown in my finished product
and personnaly like the sound of boards that have a little more compression.
This  is frankly an unprovable notion but it,s mine all mine .The truth is
everybody,s boards have compression in them or they would spilt like ripe
melons after the first midwest or eastcoast seasons.Many of my colleagues
dry there panels to 30%or 6% e.m.c.then apply ribs crowned at 60 ft. radius
they sound wonderful and hold up well in severe climates provide damp
chasers are used.I am in calif. where the climate is mostly wonderful ( eat
your heart out Ye snowbound brethren).and much of my clientle are in the
greater bay area where moderate climate are usual year round. All that to
say that you make your boards work as well as possible for the region you
are in.When I am making a board that is going to neveda I dry it down a to a
low 4.5% to 5% Emc as r.h. levels average below 40 % year round .Nev. is a
desert.My usual practice is to dry the panel to around 25%R.H. or 5.5% to5 %
and crown My ribs in the treble ,top 5 or 6, to a 60 FT. crown and in the
larger portions of the belly I cut about two thirds of a 60 ft. radius in
that area.I.E. instead of cutting say a10 m.m. amount of crown I,ll cutabout
7.5mm.With a steep crown in my press and some curve in my ribs I get a
result that I like that insures panel compression without the
destructiveness of pure forced crowning.The method I,m describing can be
found in Samuel Wolfendens book A treatise on Art of Pianoforte construction
originally produced 1916 A must read for the rebuilder.One final word ( yeah
right) I have heard wonderful sounding boards built in a variety of ways And
although it is possible to build forced crown boards( i.e. flat ribs curved
press and more drying  4% e.m.c. or less ) and be successful at  it, the
parameters are very narrow and strict adherence to a drying schedule that
works for the type of spruce your using is essential to avoid the crushing
of wood cells that leads to premature tonal loss and board failure.    Best
of success Dale Erwin  from the great central valley modesto ,calif.